If the driver store becomes corrupt, new drivers cannot be added to it and Windows may not be able to copy driver files from it . The inability to add new drivers or install new devices could therefore indicate problems with the driver store . Possible causes of driver store corruption can include:

If the files used to index the driver store are missing or corrupt, new drivers cannot be added to the driver store . The inability to add new drivers or install new devices could therefore indicate problems with these index files . Possible causes of index file corruption are similar to causes of driver store corruption . If index files become corrupt, restore them from your most recent system backup . The three index files for the driver store are Infpub .dat, Infstore .dat, and Drvindex .dat, and they are found under %SystemRoot%\Inf . You can also use System Restore to restore index files

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Understanding Device Installation and Management CHapTER 17

because these files are added to protection points, but this approach is generally not recommended because reverting to a previous restore point can affect other aspects of the system and its installed software . Restoring from backup is therefore preferred . diReCt FRoM tHe SoURCe

Troubleshooting Driver Signing Issues

Sampath Somasundaram, SDET

DMI Team, Windows

f you see a Windows Security dialog box with a check box that says Windows Can t Verify The publisher Of This Driver Software, you should verify the validity of the

driver signature by checking the following:

1 . See whether the INF file contains the CatalogFile=FileName entry and whether

the FileName matches the CaT file in the same directory.

2. If the preceding step is successful, double-click the catalog file, view the signature, view the certificate, and check the Certification path tab. Verify that the entire chain of certificates is trusted. If not, add them all to the trusted root Ca store on the local computer. The last one should be added to the Trustedpublisher store. If you see a Windows Security dialog box with a check box that says always Trust Software From Some_name, install the certificate in the Trustedpublisher store on the local computer. alternatively, you can select the check box and click Install, and the system will add the certificate automatically to the Trustedpublisher store. Note that you must use Mmc.exe to install the certificate, not the Certmgr.exe UI, because Certmgr.exe installs the certificate in the current user s store only. If the package is signed but an unsigned dialog box still shows, determine whether any older unsigned versions of the driver are in the driver store. Open a command prompt and type pnputil.exe e. To remove a driver from the driver store, type pnptuil d OEMfilename.inf, where OEMFilename.inf is the OEM file name listed by pnputil e for the driver package. To check whether the catalog file actually contains the driver files, use the Signtool.exe utility from the WDK/platform Software Development Kit (SDK) and type signtool verify /c catalogfilename filename. Finally, to determine why your new latest freshly signed driver is losing to in-box drivers, do the following:

n n n

Select the option to treat all signing as equal. Compare the date of your driver with that of the in-box driver. Check the version to see whether the dates are equal.

CHapTER 17

Managing Devices and Services

Understanding Power Management

The goal of power management in Windows is to maximize energy efficiency . This is accomplished by minimizing the amount of power used while automatically providing required performance on demand . Power management is an increasingly important issue for businesses as a result of rising energy costs and energy consumption by today's desktop and mobile computers . In the United States, the Environmental Protection Agency has estimated that PCs at home and in the workplace use about 2 percent of all electrical energy consumed . Leaving a PC on at home can add up to 8 percent to the total household power usage for the average home . By contrast, putting a PC into Sleep mode for 14 hours a day can save between 600 and 760 kWh per year of electricity consumption . In 2009, this means savings of approximately $63,000 per year per 1,000 PCs for which this is done . The business and environmental importance of improving the power efficiency of PCs is compelling, and Microsoft has made numerous enhancements in this area in Windows 7 .